Process for mining sulphur



Patented June 19, 1928..

UNITED STATES PATENT OFFICE.

WILSON T. LUNIDY AND HOMER S, BURNS, OF FREEPORT, TEXAS, ASSIGNORS TO THE F'REEPORT SULPHUR GOMIANY, F FREEPORT, TEXAS, A CORPORATION OF TEXAS.

PROCESS FOR MINING SULPHUR.

No Drawing.

Our invention relates to the process of recovery of elemental sulphur from sulphur bearing deposits by means of what is commonly known as the hot-water method or the underground .fusion method. It has for its object the better control of the movement within the sulphur bearing formation of the fusion fluid or heating medium (commonly water) used in this process.

In order that the operation of our invention and the objects thereof may be made clear We will first-describe the nature of the sulphur bearing formations commonly encountered in the United States and will also briefiy describe the 'so-called underground fusion method as now generally applied to sulphur mining.

By far the greater part of the'sulphur known toexist in the elemental form on the American Continent "occurs in the form of nearly pure crystals 'of elemental sulphur interspersed with gypsum or lime rock or mixtures of these rocks. It occurs usually in what are known as domes, which are found in considerable numbers along the coastal plane bordering on the Gulf of Mexico in the States of Texas and Louisiana.

The sulphur bearing portion of these domes,

or of such of them as are known to contain 8 sulphur, lies at depths varying from a few hundred feet up to 1500 or 2000 feet. The sulphur bearing portions of these dome formations are usually more or less porous or spongy. They contain cavities of widely varying sizes, from minute pores to cavities of very great size, which may be aptly described as caverns. These cavities are more or less inter-connected by channels through which water may circulate with a greater or less degree of freedom depending upon the number and size both of the cavities or pores, and of the inter-connecting channels. Being at considerable depth in the ground and below the water table, these cavities, pores,

channels and caverns are normally filled with water. .This water being in contact with sulphur, limestone, gypsum and other rocks and earths, contains in solution considerable quantities of mineral matter. In

different sulphur bearing formations and also in different portions of the same sulphur bearing formation, there is often to be found a great degree of variation in what may be termed the permeability of the for- 5a mation. This permeability is a function of Application filed September 9, 1926. Serial No. 134,570.

channels between the cavities. Some of the effects of this difference in permeability upon the ease or difiiculty of mining sulphur by the underground fusion method will be described later.

The recovery of sulphur from these sulphur bearing formations situated at depths of several hundred feet under the surface of the ground is commonly accomplished by what is generally known as the underground fusion process. This process consists essentially 1n forcing Water at'a high temperature, usually above 300 F., and under a res'sure usually above 100 lbs. per, square inch, into the sulphur bearing formation, and raising to the surface of the ground the sulphur melted by the water.

In the carrying out of this process holes are drilled from the surface of the ground down into and through the sulphur producing horizon. In these holes or wells are placed a series of metal ipes of various diameters, one within anotlier, in such a manner that hot water under the desired pressure and temperature conditions may be forced through the water pipes, and also that fused or melted sulphur may be simultaneously lifted to the surface through one of the inner pipes of the series.

The hot water so injected into the sulphur bearing formation passes through the pores and cavities of the formation and while so into the sulphur bearing strata passing raises the temperature of the formation with which it comes into contact. This rise, of temperature continues untilthose ,portions of the formation through which quantities of the hot water have passed reach a temperature approximately equal to that of the injected water. As pure sulphur fuses at about 240 F.,' and as the hot water is injected at a considerably higher temperature, there results a melting of the sulphur contained in the formation. This meltformation.

the purpose. This molten sulphur is then lifted to the surface of the ground by means of compressed air, utilizing the well known device known as an air lift.

As already stated, there is a wide difference between sulphur formations and also between different portions of the same formation as regards the permeability of the In some cases the pores, cavities and passages are relatively small in size and few in number and uniformly distributed throughout the formation. In other cases these cavities are much more numerous, much larger and unevenly distributed throughout the formation. In some formations it is not uncommon to find very large cavities and very open channels through which the hot water may freely pass. In the former case, where the pores, cavities and passages are small and uniformly distributed the water may find its way slowly through the openings and radiate fairly uniformly in all directions from the pipes through which it is injected into the sulphur bearing formation. This is a very desirable condition and results in a relatively complete melting of the sulphur in all directions from the pipes. In the latter case. where the cavities and passages are much larger or are irregularly distributed. it is found that the hot water finds a free and easy passage away from the pipes through channels or openings in one or more directions and a relatively obstructed and diflicult passage in other directions, the result is that only a relatively small roportion of the sulphur in the vicinity of tie pipes is melted. This often results in large and valuable portions of deposits of sulphur remaining unmelted within easy melting radius from the well .after production has ceased.

One object of our invention is to effect a more uniform distribution of the fusion fluid in all directions about the )ipes through which it is injected into the sulphur bearing formation. Another object is to regulate the resistance offered to the flow of the fusion fluid by the formation surrounding the sulphur well. Another object is to make it possible to effect a control of these conditions of distribution and resistance while the well is in operation and producing sulphur.

Under some conditions some of the objects of this invention are accomplished by the use of a fusion fluid of relatively high viscosity, as is disclosed in our co-pending application, Serial No. 127,475, filed August 5th, 1926. We have found that under conditions frequently encountered in some of the more permeable sulphur bearing formations, and also some sulphur bearing formations having permeable cap rock overlying them. it is desirable to have greater control over the distribution of the fusion fluid and the resistance offered to its flow through the formation. This we accomplish by the use of a fusion fluid having high frictional resistance to flow through a porous body.

The fusion fluid which we prefer is one composed of a suspension in water of earthy materials such as clay, gumbo, sand, gravel, shell, and the like in which there is present a considerable quantity of lumps, grains, and particles of Such size that they introduce a high frictional resistance to the passage of the fusion fluid through the porous strata of the formation. This fusion fluid is prepared by excavating the earthy materials from the ground by means of any suitable apparatus such as a suction dredge, or mechanical shovel or power digger, and so treating the excavated material with water in suitable apparatus, that the resulting fluid contains the desired proportion of lumps and particles of the size best suited for use in the particular character of sulphur bearing formation then being treated by the process. The treatment of the excavated earthy materials is so carried on that there are left in the resulting mixture, in addition to the very fine material, many lumps of clay, gumbo, sand, pebbles, ehert, shell or other material in lump or granular form. The maximum size of the lumps, granules or particles, and the proportion that they form of the total quantity of solid matter in the fluid may be varied as may be required to best suit the conditions existing in the vicinity of the sulphur well into which the fluid is to be injected.

N ot only is it desired to vary the size and proportion of lumps, etc. in the fluid injected into different wells but it is also advantageous to vary these characteristics from time to time in the operation of the underground fusion method in a single well. It is found, for example, that after a quantity of fluid containing a large proportion of large lumps, etc., has been injected into a well it is advantageous to follow it with a fluid having a lesser quantity of lumps, etc., or containing lumps, etc., of smaller size. It is important therefore that the character of the fu ion fluid be susceptible to change ans-regards its content of lumps, particles, etc., at the will of the operator. This regulation or control of the quantity and size of the lumps and particles in the fusion fluid 15 particularly advantageous in stopping off or restricting the free flow of water or other fusion fluid in a porous cap rock which frequently overlies the sulphur bearing formation. It is also useful in open, porous sulphur bearing formations even though they be of a uniform or only slightly varying degree of porosity. It is useful in such cases because of its ability to obstruct the too free passages and so set up an increased resistance to the flow of the fusion fluid which tively large lumps -or particles can be in-.

jected through suitable pipes into the porous formation and by its relatively greater frictional resistance build up the much desired pressure in the well. These varieties in the character of the fusion fluid enable us to meet the variations in the porosity of the sulphur bearing strata and of the cap rock overlying them and to produce the condi tions of frictional resitance therein which re sult in a more effective distribution of the fusion fluid and therebyproduce a greater fusion and greater recovery of the Sulphur present in the sulphur bearing formations.

We claim as new and desire to protect by Letters Patent:

1. The improvement in the process of mining sulphur by the underground fusion method which consists in injecting into the sulphur bearing formation a heated fusion fluid consisting partly oflumps of earthy materials in suspension.

2. That step in the process of mining sulphur by the underground fusion method which consists in injecting into the sulphur bearing formation a heated fusion fluid consisting partly of lumps of earthy materials in suspension in water, and then injecting a heated fusion fluid having a lesser proportion of lumps of earthy materials in suspension in water.

3. That step in the process of mining sulphur by the underground fusion method which consists in injecting into the sulphur bearing formation-a heated fusion fluid consisting partly of lumps of earthy materials 1n suspension in water and varying the proportion of lumpy earthy materials in suspension in'the fluid substantially as described.

4. That step in the process of mining sulphur by the underground fusion method which" consists in injecting into the sulphur bearing formation a heated fusion fluid consisting of lumps or particles of earthy materials in suspension, and varying the size of the lumps or particles to suit the character of the sulphur bearing formation, substantially as described.

Signed at Freeport, in the county of Brazoria and State of 'Texasthis 31st day of August A. D. 1926. 2

WILSON T. LUNDY. HOMER S. BURNS. 

